There are many problems associated with the interconnection of elements in microcircuitry. The very dimensions of an integrated circuit or chip device in a hybrid circuit would have been unbelievable only a short time ago. Consequently, new techniques must be evolved to solve the many problems of their interconnection and to improve microcircuit technology.
One of the most difficult problems is the interconnection of various hybrid elements where the ultimate terminals of a micro-miniature circuit within a chip must be electrically and physically connected to the terminals of another microminiature circuit, of the same or another chip, or to a utilization circuit or device. With terminals measured in the thousands of an inch, and with wires a fraction of the size of a human hair, the problems are very difficult, and the chances of failure are relatively high.
For one thing the wires are not, and almost cannot be, insulated. There would be no practical way of cleaning off the insulation to make a good contact, which is difficult enough without having to cope with insulation problems. And since the wires are not insulated, special care must be taken to avoid wires crossing each other, or even being positioned too close to each other.
This has led to the interconnection of hybrid circuits by means of a complicated fabrication technology. The first step being to generate the art work, e.g., make a rough drawing or lay-out of all the components and to arrange them in such a way that the shortest lines are used and there are a minimum number of crossovers. The design is then laid out accurately, using a computer graphic design system which generates a photo-mask that is used to make the actual substrate circuit, with metallized interconnecting lines.
This ultimately produces a complex network of interconnections, extending over very much more area than the chips themselves, just to come up with adjacent contact points. These networks of lines also add undesirable capacitance, inductance, and resistance to the overall circuit; besides the waste of space.
The hybrid elements or chips are mounted on the substrate in their proper positions with respect to the interconnecting lines and the bonds must be made from a metallized chip pad to a terminal at one end of a metallized line and then from a terminal at the other end of the line to another metallized chip, pad or component terminal, and so on until all the components have been interconnected. This may require as many as three or four bonded interconnecting wires for one actual point-to-point contact.
There are other methods for insulating the interconnecting wires in the finished product; such as by evaporating insulation on the finished surface, or by encapsulating the entire substrate, but these must all be done after the wiring is completed, and short circuits in complex or close wiring may have occurred during the assembly process.
It is therefore an object of this invention to provide a system for insulating very-fine interconnecting wires as they are being connected from one terminal to the next so that wires can be crossed or placed in close proximity and hybrid elements can be directly interconnected without danger of shorting of the interconnecting wires. It is a further object of this invention to provide a system that can eliminate the complex networks of lines and multiple interconnections necessary in the existing systems. It is a further object of this invention to provide a system that permits side by side placement of hybrid elements to reduce the overall size of hybrid circuits.